The present invention relates to a method for treating non-woven polyester, rayon, nylon or combinations of like fabrics for use in the manufacture of automobile tires and accessories such as V-belts, bead wrap, chafer strips and the like, in order to improve the adhesion qualities and overall strength of such fabrics.
It is a common practice in the manufacture of pneumatic tires, particularly automobile tires, to incorporate a chafer strip into the bead area of the tire to provide a sealing and seating surface on the tire bead which can be engaged to the rim of a wheel. Generally, such strips extend from an inner surface area of the annular tire bead to an outer surface area. Because of the relatively high stress conditions imposed at or near the bead area of automobile tires during normal use, non-woven fabrics presently available tend to split, resulting in a loss of sealing capability and tire failure. Such failures are due primarily to a lack of adhesion between the strip and tire surface and/or to the inadequate construction of, for example, the chafer strip itself. In the case of tubeless tires, both the sealing and seating functions of a chafer strip are of critical importance in ensuring prolonged tire safety and performance.
The splitting and deterioration problems of non-woven fabrics used in the manufacture of automobile tires and accessories is not limited to chafer strips. Under high stress conditions, similar problems are known to exist in the construction of conventional bead wrap and so-called "cushion" fabrics used to produce a variety of V-belts such as fan belts, air conditioning belts and the like. In all such cases, the splitting and deterioratiofn problems have generally been traced to the lack of cohesive strength in the body of the non-woven fabric and the surface of the bonded rubber component.
As an alternative to the use of woven fabrics, non-woven fabrics have been produced having desired extension characteristics when cut into long lengths so that a single length will form, for example, a complete chafer strip area of a bead. However, many of the known non-woven fabric constructions have proven unacceptable for chafer strip or bead wrap applications because of the limitations of the adhesive binder in the non-woven fabric. Typically, such strips are manufactured by overlaying thin sheets of web (usually at 90.degree. angles to each other), bonding the sheets with certain known adhesives to form a laminated-type structure, and then drying the fabric in a heated environment. During the drying operation, however, the adhesives tend to migrate to the top and bottom surfaces of the non-woven laminate, leaving fiber layers in the interior which are bonded to a lesser degree than layers near the outside surfaces. The migration tendency of such fabrics often results in a delamination of the non-woven strip under normal use conditions, causing splitting or a premature loss in its strength and sealing characteristics. In addition, the laminated-type structures are more vulnerable to the relatively severe manufacturing process conditions encountered during subsequent production of the tire itself.
It is also known that chafer, bead wrap and V-belt products may be constructed from non-woven fabrics which are "spunlaced" or "tanglelaced" from staple fibers of any natural, cellulosic, or synthetic materials. The fibers of spunlaced fabrics, for example, are held together by random intangling and interlacing without any heat bonding of individual fibers, and are generally produced by processes using high energy fluid jets, such as those disclosed in U.S. Pat. Nos. 3,434,188; 3,485,706; 3,485,708; and 3,508,308. However, such methods, in addition to their increased expense of operation, require complex processing equipment and have not resulted in chafer strip or bead wrap constructions which are free from splitting, cracking or other deterioration under high stress conditions.
It has now been found that non-woven fabrics used in the manufacture of V-belt, bead wrap and chafer strip constructions may be produced such that their strength and adhesion qualities are significantly improved, thereby eliminating the premature splitting and deterioration problems associated with conventionally available products. In particular, it has been discovered that such fabrics may be treated with an adhesive system that will allow the subsequent bonding of an impregnating elastomeric polymer or other bonding composition (preferably compounded natural rubber) to the fibers of the non-woven fabric to thereby prevent such fabrics from splitting or deteriorating during prolonged use. In addition, the method according to the present invention results in fabric constructions that do not exhibit the adhesion problems associated with conventional prior art products.
In essence, the process according to the invention comprises the steps of pretreating of a non-woven fabric with an isocyanate compound; drying the fabric in a heated, closed environment to a maximum moisture content of 1 percent or less solvent media; applying a resorcinol/formaldehyde/vinyl pyridine adhesive (commonly known as "RFL"); subjecting the fabric to a second drying operation; and impregnating the non-woven fabric with a solvent solution of compounded natural rubber. Where applicable, the isocyanate step may be followed with the application of an elastomer such as neoprene, foregoing the applicaton of RFL. Also, the isocyanate step may be directly followed by an elastomer without drying the isocyanate before the application of the impregnating compound and subsequently drying the entire matrix.
The present invention is, therefore, a marked deviation from prior art laminated-type structures in that it results in a single, non-woven fabric having strength and adhesion characteristics due to a high degree of bonding between the non-woven fibers and impregnating compound. That is, the claimed construction, unlike laminated products which allow the adhesive compound to migrate to the top and bottom surfaces of the fabric, results in a non-woven chafer strip, bead wrap or V-belt fabric which is thoroughly and uniformly impregnated with the bonding material. It is this high degree of impregnation of the end product (i.e. of the treated non-woven fabric) which contributes to the unexpected increase in stability and strength of the fabric after it is bonded to a rubber surface and integrated, for example, into a pneumatic tire. The complete impregnation of the non-woven fabric effectively eliminates the deterioration problems associated with previously available non-woven fabric constructions used in the manufacture of pneumatic tires and forms a stronger, more cohesive structure having little or no tendency to split or separate, either within itself or from rubber or elastomeric materials to which it is subsequently bonded. The method and fabric according to the invention also provide a superior finishing strip for tire beads, particularly tubeless tires which must maintain an air-tight seal around the bead areas. Further, the uniform characteristics of cohesion and strength are not affected by subsequent tire manufacturing operations.
Thus, it is an object of the present invention to provide a method for treating non-woven fabrics used in the manufacture of automobile tires or V-belts in order to improve the adhesion qualities of such fabrics and to thereby eliminate their tendency to split or deteriorate under normal use. It is a further object of the present invention to provide for improved bead wrap, V-belt and chafer strip constructions for non-woven fabrics. Other features, objects and advantages of the subject invention will appear more fully from the following description of illustrative examples.